Analysis Of CfrA Gene-ferric Enterobactin Receptor Of Campylobacter Jejuni

Objective:By comparison of CfrA, ferric enterobactin receptor gene sequences of Campylobacter jejuni strain, to analyze the features of nucleic acid and amino acid sequence, detect the characteristics of CfrA genetic mutation bases, secondary structure, and hydrophobicity, speculate the possible conservative section and highly variable section, and analyze the relationship of genetic evolution as the basic data of study on C.jeuni vaccine.Methods:We selected and cultured 3 GBS-associated C.jejuni strains named zhanxing strain, lulei strain, and qiaoyuntao strain, confirmed as GBS-associated by animal model test, isolated from faeces of GBS patients in Neurology Department at the Secondary hospital of Hebei medical university , China. After sequencing the genome sequences of them, each of the results were spliced and assembled into a complete sequence by the terminals overlapped each other. The 3 cfra sequences were compared with the corresponding sequence of NCTC11168 in GenBank to find the base and amino acid mutations, the change of secondary structure, and also construct phylogenic relationship with bioinformatics software, such as SequenceAlignment, DNASTAR Editseq, MegAlign, and Protean.Selecting 12 C.jejuni strains from NCBI, measured the gene sequencing of cfra, grouped in terms of genetic tree. The 12 cfra sequences were compared between the groups to speculated the possible conservative section and highly variable section, the change of secondary structure, and also construct phylogenic relationship with bioinformatics software, such as SequenceAlignment, DNASTAR Editseq, MegAlign, and Protean.Result:The cfra genes of zhanxingstrain,, lulei strain and qiaoyuntao strain all have 2091 base pairs. Compared with the C.jejuni strain NCTC11168, mutation rate was 0%, 1.4%, and 1.3% respectly. No significant changes in hydrophobicity. The phylogenic analysis demonstrated that the highest genetic distance was 1.6% existing between zhanxing and lulei strains . The eight genes of 12 C.jejuni strains from NCBI all have 2091 base pairs. The remaining four strains: (1)C. jejuni subsp. jejuni 84-25 gcj8425₁3(2)C.jejuni subsp. jejuni 260.94c_jejuni_subsp_jejuni₂6094₄0(3)C.jejuni subsp. doylei 269.97(4) C.jejuni subsp. jejuni CG8421 C493, exist insertions and deletions. The maximum base variation rate was 6.79%. The base variation segment were: The first group had a high degree of similarity, the high variability section was 6-147aa; The second group mutation rate was high, the variation segment was 1-1008aa and conservative section was in 1059-2075aa. The third group had high variation. The changes of protein secondary structure were: Group 1 ,5-54, 524-692 ; Group 2 1-24 520-692. The possibility of each section in the surface was smaller. Hydrophobicity were not significantly changed. The phylogenic analysis demonstrated that the highest genetic distance was 5.5%, between C. jejuni strain S3B and C. jejuni strain M76297.Conclusion:In addition to four strains, 11 strains all showed high conservative property. Alignment of complete CfrA sequences from 12 Campylobacter isolates showed that the levels of amino acid identity for CfrA range from 93% to 100%. Smaller genetic distances of Zhanxing strains, lulei strain and qiaoyuntao strain showed evolutionary clustering phenomenon of the C.jejuni strains and demonstrate that the C.jejuni strains have its regional features in Hebei province. Consideration of the high mutation rate of group three, we speculate that there is a novel ferric enterobactin receptor or system for ferric enterobactin-mediated uptake. This possibility remains to be examined in future studies. In conclusion, these findings strongly suggest that CfrA is a promising vaccine candidate for preventing and controlling Campylobacter infection in humans and animal reservoirs.